Hydraulic systems, such as those found in work machines, employ a hydraulic cylinder to raise and lower relatively heavy loads and at times to support such loads in an elevated position. A hydraulic valve may be provided in the hydraulic system on the work machine to prevent movement of the cylinder to support the load in the elevated position in the event of a loss of the hydraulic system, such as by trapping hydraulic fluid in the cylinder to prevent the cylinder from retracting. The valves may be used in combination with a locking device to prevent movement of the function. A pilot pressure is applied to open a poppet of the valve to allow fluid flow through the valve. Removal of the pilot pressure will allow the valve to close, preventing fluid flow through the valve.